Allow to compact header in allocation-profile

runtime/observatory/lib/src/elements/css/shared.css

Index: runtime/observatory/lib/src/elements/css/shared.css
diff --git a/runtime/observatory/lib/src/elements/css/shared.css b/runtime/observatory/lib/src/elements/css/shared.css
index e1ce97796912aeaac511e338f43bc9dcb784bff6..9e6defc2859e8acecd7535cf0188c101d4af0d6f 100644
--- a/runtime/observatory/lib/src/elements/css/shared.css
+++ b/runtime/observatory/lib/src/elements/css/shared.css
@@ -391,6 +391,18 @@ allocation-profile .heap-space.right .legend * {
   direction: rtl;
 }
 
+allocation-profile .compactable {
+  position: relative;
+}
+
+allocation-profile .compact {
+  position: absolute;
+  bottom: 20px;
+  left: 50%;
+  width: 8em;
+  margin-left: -4em;
+}
+
 allocation-profile .heap-space.right * {
   direction: ltr;
   text-align: right;
@@ -437,6 +449,10 @@ allocation-profile .collection {
   top: 560px;
 }
 
+allocation-profile .collection.expanded {
+  top: 160px;
+}
+
 allocation-profile .collection-item {
   box-sizing: border-box;
   line-height: 20px;